(1) Field of the Invention
The present invention relates to a centrifugal compressor, and in particular to a dry gas seal system thereof.
(2) Description of Related Art
Examples of conventional dry gas seal systems for use in a centrifugal compressor are disclosed in JP-A-9-60734, WO 01/007791 A1, and JP-A-11-182690. In the dry gas seal system disclosed in JP-A-9-60734, to collect process gas leaked from a temporary seal of a dry gas seal for preventing environmental contamination, and to save resources, a small-sized compressor is installed to a leak gas line of the process gas leaked from the temporary seal of the dry gas seal. Furthermore, a cushion tank keeping a pressure balance is installed on a suction side of the small-sized compressor. The process gas whose pressure is increased is returned to a process gas line by the small-sized compressor.
The dry gas seal system disclosed in WO 01/007791 A1 is equipped with a primary dry gas seal and a secondary dry gas seal. The working gas leaked between a rotor and a rotary ring is detected by a pressure switch and a flow meter installed in a primary seal ventilation line. The working gas leaked from a labyrinth seal and the secondary dry gas seal is exhausted to the outside of a machine together with a purge gas.
The dry gas seal system disclosed in JP-A-11-182690 handles volatile fluid. A drain hole is provided between a mechanical seal and a dry seal, and a collection pipe is connected with the drain hole. The collected fluid is overheated and evaporated by a steam pipe, introduced to a flare, and treated by combustion.